Papermaking process utilizing modified locust bean gum



Patented July 7, 1953 UNITED STATES PATENT" OFFICEf Y PAPERMAKING PROCESS UTILIZING MODI- FIED LOCUST BEAN GUM Nat Frisch, White Plains, and Frank J. Sweeney, Forest Hills, N. Y., assignors to stem, Hall &

. Company, Inc., New of New .York

York, N. 'Y., a corporation No Drawing. Application June 26, 1951,

Serial No. 233,698

speed up the paper making process and to increase the strength of the paper formed thereby. Thus, for example, it has been proposed toincorporate into the paper stock. locust bean gum or flour prepared. from the seed endosperm of the locust or carob tree (Ceratonia siliqud), a perennial legume native to the Mediterranean region. 'The fruit of this tree is in the form of pods. It wasknown to the ancients as manna and in later periods has been known as St. Johns bread. The gum powder generally, known as locust bean gum is obtained fromthe seeds in these pods and has been utilized heretofore as a film forming material in textile sizing and as a thickening agent in printing and dyeing.

It is known that the addition of locust bean gum to paper stock will result in paper having improved wet and dry strength characteristics. The use of locust bean gum in the manufacture of paper has,'however, been discouraged due to the considerable diificulty involved in uniformly distributing the locust bean gum throughout the aqueous furnish. Even when special equipment in the form of injectors and high speed stirrers is used and the locust bean gum'is added slowly to water, an appreciable proportion of the locust bean gum will remain in the form of lumps even after cooking. If these lumps get into the sheet they cause fisheyes and later cause a breakdown in the sheet. Special equipment must therefore be utilized to strain out these lumps,'which incidentally result in a waste of locust bean gum, and the tanks in which the gum is mixed and cooked must frequently be drained and cleaned. The additional equipment required and'the precautions that must be followed in order to incorporate locust bean gum in paper stock have substantially offset the ad-- vantages obtained by use of the gum with the result that the use of locust bean gum in the fan pump or stock regulator box, and aqueous solution of a combination of locust beangum;

a sodium borate and an. acid material selected from the group consisting of glyoxal, pyruvic aldehyde, ammonium chloride, citric acid, boric acid and aluminum sulfate prepared preferably by the cooking operations subsequently disclosed.

This method avoids the difficulties involved in adding straight locust bean gumto the furnish, significantly improves the paper making process andresults in improving the characteristics of the paper produced thereby. I

The aqueous solution of a combination of locust bean gum,. borate and an acid material can be prepared with utmost facility in any one of a number of ways. A dry mixture of locust bean gum, borate and acid material may be dispersed readily in coldwater or a dry mixture of locust bean gum' and borate may first be dispersed in cold water and the acid material added to the aqueous dispersion so formed. Neither'of these;methods results in the formation of objectionable lumps and the complete dispersion of duced from a given stock. The utilization of this.

invention, forexample, has made it possible to increase the capacity of a mill having limited drying facilities without reduction in salient properties by making it possible to use'stock of increased freeness thereby permitting a greater amount of water to drain from the web during passage over the wire prior to drying. Also the capacity of a mill to produce a uniformly good quality paper has been increased in view of the improved web formation from mediocre or poor stock. Thus, for example, it has been found that the method of adding a combination of locust bean gum, borate and acid material to the furnish makes it possible to reduce the proportion of relatively expensive sulfite pulp and increase the proportion of relatively inexpensive groundwood without deleteriously affecting the characteristics of the paper produced thereby or slowing down the speed of .the web. Normally suchstandar-d final quality could be obtained only by a relatively slow operation. In connection with mill operations having good drying capacity and utilizing relatively good starting stock, it has been found that gradients used in the combination have considerable effect upon the results obtained in so far as handling and dispersibility are concerned. As the proportion of locust bean gum in the combination is decreased, the ease with which it can be dispersed in water is increased. On the other hand, as the proportion of locust bean gum in the combination approaches 100%, it becomes more difiicult to disperse in water and more liable to form lumps that must be strained out prior to the addition of the solution to the furnish. As a practical matter, the presence of less than about 50% locust bean gum in the combination is too little to obtain the full benefits derived from its use and the presence of more than about 96% of the gum will result in sufficient dispersing dimculties to make its use uneconomical. It is generally preferred therefore to limit the proportion of locust bean gum in the combination to between about 65% and 93%. Optimum results have been obtained with concentrations ofbetween 85% and 90%. 7

Changes in the relative proportions of borate and acid material also have a considerable effect upon the results obtainedin the paper making operation and more particularly upon the consistency and characteristics in the aqueous solu tion formed when the combination is added to water and cooked. The borate tends to impart to the cooked solution a heavy body, high film strength and stringiness. The acid material reduces the ropiness of the cooked solution, imparts a long stringy character thereto and reduces its viscosity to a level that makes handling of the solution practicable.

It has generally been found desirable to adjust the relative V proportions of locust bean gum, borate and acid material so that the dispersion thereof in water before cooking or the solution thereof after cooking will have a pH between about 3 and 10. The lower limit of the pH range is determined by the characteristics of the particular locust bean gum in the combination and particularly by its ability to .open or become gelatinized when cooked. If the pH is reduced to a value below about 3, it becomes extremely difiicult, and in some cases impossible, to gelatinize the locust bean gum by cooking. The upper limit of the pH range is determined by the viscosity of the cooked solution. It is essentialin practice that the cooked solution be not so viscous that it cannot readily be transferred from a cooking vessel to a supply vessel or from a supply vessel to the head box, fan pump or stock regulator box. Reduction of the viscosity simply by diluting the solution with water is'not practicable because that would involve increasing the capacity'of the cooking vessel or supply tank and of the pumping equipment utilized to add the cooked solution to the furnish. It is preferable therefore to maintain the pH between about '3 and so that the cooked solution will not be too viscous and at the same. time not too acid to prevent or inhibit gelatinization of the locust bean gum. While it is possible to carry out the process of this invention at either extreme pH value, it has been found that optimum results are obtained by maintaining limited range, the locust bean gum will become gelatinized quite readily and the viscosity of the cooked solution is sufficiently low to permit easy transference'of the cooked solution from a supply source to the head box, stock regulator box, fan pump, or to any otherpoint at which the combination is added to the furnish. Satisfactory viscosity and gelatinization conditions are normally obtained by maintaining the ratio of borate to acid material at between about 12.1 and 3:1 and preferably at about 2:1.

A mixture that has been found to be particularly successful is one containing 85% by weight of locust bean gum, 10% by weight of borate and 5% by weight of, acid material, When a handful of this mixture is' simply dumped into cold water, it at first floats on the surface. Within a few seconds, however, the mass of material breaks up into smaller portions which fall to the bottom until all of it has left the surface of the Water: Simple stirring of the water will thereupon form a uniform dispersion of the material which, upon being cookedi-to a temperature of about 200 FL, will form a-viscous, stringy and transparent solution.

By Way of contrast, hen straight locust bean gum is dumped into cold water, only a small portion of it may fall to the bottom and most of the locust bean gum remains floating on the surface The outer portions of the mass apparently absorb wateryswell and become sticky so as to form a coating that denies access of water to the interior of the mass. Vigorous-stirring fails to produce a uniform distribution of the gum throughout the water and cooking thereof at 200 F. results in a syrupy mass containing lumps which must be removed before it can be added to the furnish.

When it is desired to employ mixtures having concentrations of locust'bean gum that are less than about starch may be added to make up for the lack of locust bean gum. Thus, for example, favorable results have been obtained with a mixture consisting of 68% locust bean gum, 17% starch, 10% borate and 5% acid material. Small amounts of oxidizing agents, such as barium peroxide and sodium perborate may be added to thin out the solution prepared when the combination is dissolved in water. 7

The borate may be any suitable borate such as, for example, sodium tetraborate (borax) and sodium metaborat'e. I 1' The acid material may be glyoxal, pyruvic aldehyde, ammonium chloride, citric acid, boric acid or aluminum sulfate or a combination of one or moreiof said materials; The presence of glyoxal or ammonium chloride in the combination is particularly desirablebecause they both promote an extremely rapid and facile dispersion of the mixture in cold Water. A; mixture consisting of locust bean gum, 10% borax and 5% glyoxal, for example, will readily and completely disperse in w-ater'at room temperature in as little as 'Zseconds. ;If ammonium chloride is used instead of the glyoxal, the mixture Will dis-.

perse under the same conditions andin the same manner in as little as 9,6 seconds. therefore is preferable from the standpoint of rapidity of dispersion whereas ammonium chloride is preferable from the standpoint of economy inasmuch as the price of ammonium chloride is much lower thanthat of g1yoxal.

I Aqueous solutions containingfrom about 4% Glyoxal up to about by weight of solute may readily be prepared.

In accordance with the preferred practice, a 1% solution of the mixture is made by adding it, in the form of a dry powder, to one half the required amount of water while the water is cold, then cooking to 200 F. and finally adding the remaining water required to produce a 1% solution, This solution is then added to the pulp in the head box, at the fan pump or in the regulator box at a rate sufiicient to add from about 1 to 20 or 30 lbs. of the mixture, based on the dry weight thereof, to a tonof furnish, likewise based on the dry Weight thereof. As in ordinary paper making processes, the concentrated stock, consisting of a maximum of approximately 4% solids, is diluted at the fan pump to a much more dilute state, e. g., 0.5%. a

The addition of a solution of locust bean gum, borate and acid material to a paper stock per- -mits increasing the freeness of the stock, reducing the power consumption in the refining phases and the steam consumption in the dryer section, all of which makes possible an increase in the speed at which the paper is run off, and generally improves the characteristics of the paper produced at a given set of machine conditions.

A number of typical formulae are listed in the tables below, the numerals therein referring to percentages by weight. 1

TABLE 1 Formula No thenadding sufficient additional Water'to bring the concentration oflsolids down to 1% by A number of paper making runs, on a laboratory scale, corresponding to the number ofsolutions-prepared, were then made. In each run, one of the prepared solutions was added tothe furnish at a rate of 10 lbs., based on the dry weight, of solution to a ton of furnish, likewise based on the dry weight.

Two sheets each having a weight of 2.8,grams were selected from each run to elimin-atetest errors due to variations in the weight of the sheets produced and each sheet selected was subjected. to ten Mullen tests. The averages of the twenty Mullen tests in each run are tabulated below:

Average Mullen Count Formula No. 7

Locust Bean Gum Alone Pyruvic Aldehyde Ammonium Chloride Formula N0 15 Locust Bean Gum".-. Powdered Potato Starch TABLE 3 Formula No 22 Locust Bean Gum Borax Glyoxal Ammonium Chloride. Boric Acid In order to further illustrate the invention without, ihowever, intending to limit it scope thereto, the following examples are included.

Example 1 Four batches of locust bean gum, borax and Example 2 Dry mixtures corresponding to Formulae Nos. 7, 8, 9, 10, 11, 13, 14, 16, l8, l9 and 20.Were made up, on a laboratory scale into 1% aqueous solu tions by dispersing one part by weight of each .dry mixture in about 50 parts by weight of water, cooking the resulting dispersions to 200 F. and then adding sufficient additional water to bring the concentration of solids down to 1% by weight. The temperature of these solutions was maintained at about 180 F.

A number of paper making runs on a laboratory scale were then made. In each run, a number of blank and modified paper sheets were made. The blank sheets were made without adding a locust bean gum containing solution to the furnish and the modified sheets were made by adding one of the prepared solutions at a rate of 10 lbs., based on the dry weight, of solution to a ton of furnish, likewise based on the dry weight.

Blank sheets 7. 1 Two blank sheets and twomodifledsheet. each having a weight of 2.8 grams were selected from each run to eliminate test errors due to variations in the weight of the sheets produced and each sheet selected-was subjected to ten Mullen tests. The averages of the twenty Mullen tests conducted on each set of two sheets are Example 3 A dry mixture consisting of 84 parts by weight of locust bean gum, 11 parts borax and 5 parts boric acid (Formula No. 24) was made up, on a laboratory scale, into a 1% aqueous solution, in the same manner as described in Example 2. H A number of blank and modified paper sheets were made and subjected to Mullen tests, likewise as described in Examples 2. In addition, modified paper sheets were made by adding the prepared solution at a rate of 5 lbs., based on the dry weight, of a solution to a ton of furnish, likewise based on the dry weight. These modified sheets were likewise subjected to Mullen tests.

Two blank sheets and the two modified sheets,

each having a weight of 3.0 plus or minus .01

gram were selected from each run to eliminate test errors due to variations in the weight of the sheets produced and each sheet was subjected to ten Mullen tests. The average of the twenty Mullen tests conducted on each set of two sheets, as well as the average percentage increase in Mullen strength of the modified sheets, are tabulated immediately below:

Percent Lucrease Average Mullen Modified sheets lbs/ton) Modified sheets (5 lbs/ton) We claim: 5 a

1. In a process of 1 making paper from an aqueous suspension of fibrous materiaLthe step which comprises adding, to said suspension, after all operations designed to substantially modify the fibrous constituents by mechanical means are completed and prior to the formation of the web, an aqueous solution of a cooked mixture of locust bean gum, a sodium borate and boric acid, the gum "being present in the mixture in an amount from" at least 1 about equal to the com bined weight of borate and acid to about 9.6% of the mixture, the .relative proportions of the borate to the acidranging from about 3: 1 to 1:1 by weight, and the amount of .cookedmixture of gunrborate and acid in the solution ranging from an'appreciable amount upto about lbs. per ton 'of fibrous material in the aqueous suspension, both based on the dry weight thereof.

2. In a process of making paper from an aqueous suspension of fibrousmaterial, the step which comprises adding, to said suspension, after all operations designed to substantially modify the fibrous constituents, by mechanical means are completed and prior to the formationof the web, an aqueous solution of a cooked mixture containing from 50 to 96 parts by weight of locust bean gum, from 2 to parts by weight of a sodium bo-rate and from 1 to 20 parts by weight of boric' acid, .the. amount of cooked mixture of gum, borate and acid in the solution ranging from an appreciable amount up to about 30 lbs. per ton of fibrous material in the aqueous suspension, both based on the dry Weight thereof.

3. In a process of making paper from an aqueous suspension of fibrous material, the step which comprises adding, to said suspension, after all operations designed tosubstantially modify the fibrous constituents by 'mechanical means are completed and prior to theform ation' of the web, an aqueousqsolution of a cooked mixture containing from 85 to 90 parts by weight of locust bean gum, from 5 to 1.0 parts by weight of a sodium borate and from to 6 parts by weightof boric acid, the amount of cooked mixture of gum, -borate and acid in the solution ranging.

' from an appreciable amountup to about .30 lbs.

. .NAT FRISCH.

' FRANK J. SWEENEY.

References Cited in the file of this patent UNITED STATES PATENTS Number V Name V 7 Date 7 60,635 Irving et al. Dec. 18, 1866 1,106,335 Pinel Aug. 4, 1914 80 61 l ;OW-}-.-'-j-1- --L--'--- Oct 8 1,334,356 Dunham Mar..23, 1920 1,448,847 Kaiser I'Mar. 2.0, 1923 --1,839,3'46-- Seferiadis 1-- Jan. 5,:1932' 2,144,522' Braun June 17,1939 2,258,628 Smith Oct. 14, 1941 2,336,367 Osborne" Dec. 7, 1943 FOREIGN PATENTS Number Country Date 508,135 Great Britain June 27, 1939.

per ton of fibrous material in the aqueous suspension, bo'th based on the dry weight thereof.

OTHER REFERENCES Broadbent et al., Tech. Supplement to Worlds Paper Trade, Review June 27, 1941, pp. 49-56.

Mason, Chemical, Industries, Jan. 1944, pp. 66 and 6'7. 

3. IN A PROCESS OF MAKING PAPER FROM AN AQUEOUS SUSPENSION OF FIBROUS MATERIAL, THE STEP WHICH COMPRISES ADDING, TO SAID SUSPENSION, AFTER ALL OPERATIONS DESIGNED TO SUBSTANTIALLY MODIFY THE FIBROUS CONSTITUENTS BY MECHANICAL MEANS ARE COMPLETED AND PRIOR TO THE FORMATION OF THE WEB, AN AQUEOUS SOLUTION OF A COOKED MIXTURE CONTAINING FROM 85 TO 90 PARTS BY WEIGHT OF LOCUST BEAN GUM, FROM 5 TO 10 PARTS BY WEIGHT OF A SODIUM BORATE AND FROM 2 TO 6 PARTS BY WEIGHT OF BORIC ACID, THE AMOUNT OF COOKED MIXTURE OF GUM, BORATE AND ACID IN THE SOLUTION RANGING FROM AN APPRECIABLE AMOUNT UP TO ABOUT 30 LBS. PER TON OF FIBROUS MATERIAL IN THE AQUEOUS SUSPENSION BOTH BASED ON THE DRY WEIGHT THEREOF. 